The invention relates to a balance shaft for a multi-cylinder, in-line engine with at least two imbalance weight sections and at least one bearing structure, with the imbalance weight sections being arranged symmetrically relative to the bearing structure and at least one of the imbalance weight sections being connected to a further shaft section at an end facing away from the bearing structure.
From German patent application DE 199 47 271 C1, a balance shaft for a multi-cylinder in-line engine is known that has two imbalance weight sections. The two imbalance weight sections are symmetrically arranged on either side of a central bearing structure. Two further bearing structure are each arranged to the right and left of the imbalance weight sections. A further shaft section extends up to a front end of the engine, is supported on a fourth bearing structure and carries a drive wheel at its free end.
The problem with balance shafts is that they deform at high speed due to the resulting centrifugal forces and are thus also bent in the area of the bearing. This can lead to tilting of the bearings of the balance shaft causing increased bearing stress. To compensate for tilting of the bearing structures, they are slightly spherical. This, however, leads to a reduced load-bearing capacity of the bearing positions. With a symmetrical arrangement of the imbalance weight sections with respect to a bearing structure the tilting of the bearing structures in operation can be reduced.
From German patent application DE 37 05 346 C2, a balance shaft for a multi-cylinder, in-line engine is known where tilting of the bearing structure in operation is to be avoided by an appropriate asymmetric design of imbalance weight sections of a single imbalance mass on the right and left of a central bearing position, with a total of two further bearing positions being arranged to the right and left of the central bearing position that are spaced at a different distance from the central bearing position. The imbalance weight section, arranged at a relatively large distance between the bearing positions, is stronger than the other imbalance weight sections in order to achieve a symmetric deformation of the shaft immediately right and left of the central bearing structure when the balance shaft is rotating.
From German patent application DE 33 14 801 C2, a further balance shaft for a multi-cylinder, in-line engine is known where imbalance weight sections are arranged symmetrically with respect to a bearing structure. A free end of the balance shaft is formed by an imbalance weight section.
It is the object of the present invention is to provide a light balance shaft with bearings which have a high load-bearing capacity.